1. Field of the Invention
This invention relates generally to copiers having recirculating document sheet feeders capable of presenting sheets of simplex or duplex documents to an exposure platen in a manner which enables the copier to reproduce collated sets of copies; and more particularly to such copiers which are capable of automatically recovering from a feeder paper jam by rearranging document sheets in the feeder hopper once a jam has been cleared.
2. Description of the Prior Art
Jam recovery procedures maintain the integrity of the run in progress while feeder paper jams are cleared. The procedures allow the the copy run to restart at the position where the trouble was encountered.
There are various types of recovery procedures in the prior art. For example, commonly assigned U.S. Pat. No. 4,078,787, which issued on Mar. 14, 1978 to L. E. Burlew et al teaches a recovery technique for copiers having only simplex capabilities, wherein the operator removes all document sheets from the feeder, rearranges them to their initial order, and replaces them in the feeder hopper. The feeder then circulates the document sheets to the proper position; i.e., until the sheet corresponding to the one which was being brought to the exposure platen at the time of the jam is at the bottom of the stack; whereupon copying resumes. Alternatively, the operator could just remove the jammed document sheets, and place them on top of the stack; the feeder thereupon cycling the sheets to the proper position.
U.S. Pat. No. 4,327,993, which issued on May 4, 1982 to J. F. Gauronski et al, teaches a recovery procedure in copiers having double-pass duplexing capabilities. In double-pass duplexing, the even numbered (back) side of each document sheet is copied onto a set of copy sheets, which are then stored in a duplex buffer tray. The document sheets are inverted before they are returned to the stack so that their odd numbered (front) sides can be copied onto the stored copy sheets during the second pass. If a jam occurs in the recirculating document feeder, recovery is accomplished by means of the operator clearing the feeder's document sheet path and restacking the document sheets in the hopper in their original order. The feeder then circulates the sheets until the document sheet side corresponding to the one which was being brought to the exposure platen at the time of the jam is at the bottom of the stack.
Single-pass duplexing enables a copier to reproduce collated sets of duplex documents at maximum reproduction rates by circulating document sheets seriatim from the hopper, and, using a turn-over mechanism, copying both faces before returning the sheet to the feeder hopper. Such a system is employed in the Ektaprint 300 copier-duplicator manufactured by the Eastman Kodak Co., and is disclosed in commonly assigned, U.S. patent application Ser. No. 862,854 filed on May 13, 1986 in the names of J. E. Smith et al. During each circulation of the document set except the last such circulation, after both sides of each sheet are exposed, each sheet is returned to the hopper with its facial orientation being reversed with respect to its initial facial orientation in the hopper. If a jam occurs in the recirculating document feeder, recovery is accomplished by the operator clearing the feeder's document sheet path and restacking those and the document sheets in the hopper in their original order and facial orientation.
Returning the document sheets to their original order and facial orientation is not an easy task. Each document sheet (including the entire stack) must be inspected and, if necessary, flipped manually so that its odd numbered, front side faces up. This is a time consuming operation when the set comprises many document sheets.